1. Field of the Invention
The present invention relates to a control channel transmission/reception method and apparatus of a wireless communication system. More particularly, the present invention relates to a method and apparatus for transmitting/receiving control channels using a resource allocation scheme that is applicable regardless of reference signal transmission or whether the reference signal is transmitted in a distributed transmission mode or a localized transmission mode.
2. Description of the Related Art
In a Long Term Evolution (LTE) system, the control channels include a User Equipment (UE) control channel and a relay control channel. The UE control channel is a control channel using a Common Reference Signal (CRS) which is transmitted as segmented in the time domain and distributed across the entire band. A control channel (e.g., a Physical Downlink Control Channel (PDCCH)) is mapped to a plurality of Control Channel Elements (CCEs), and a CCE comprises a plurality of Resource Element Groups (REGs). The control channels are interleaved in unit of REG and multiplexed across the entire band.
The relay control channel is the control channel transmitted on a specific frequency band (e.g., a Physical Resource Block (PRB)), and supports both the CRS-based transmission scheme and a Demodulation Reference Signal (DMRS)-based transmission scheme. Similar to PDCCH transmission, the control channel multiplexing supports both the REG-based distributed transmission and a PRB-based localized transmission with the notification to the relay through higher layer signaling.
In contrast to the localized transmission which is performed using both the CRS-based transmission scheme and the DMRS-based transmission scheme, the distributed transmission is performed only in distributed transmission mode. In contrast to the CRS-based transmission in which the relay performs channel estimation and channel feedback based on CRS, the DMRS-based transmission is performed in such a way that the channel estimation is performed based on DMRS while channel feedback is performed based on the CSI-RS.
Accordingly, when the CSI-RS is transmitted in the localized transmission mode, the resource amount for control channel in a PRB reduces as much as the CSI-RS. In the distributed transmission mode, because no CSI-RS is transmitted, the control channel is transmitted on the REGs at predetermined positions of a plurality of PRBs.
The Enhanced PDCCH (E-PDCCH) is the channel designed for transmitting the control channel at a specific frequency region as the relay control channel and transmitted only with DMRS in any of the distributed and localized transmission modes. Because E-PDCCH supports the DMRS-based distributed transmission unlike the relay control channel, E-PDCCH is always required to transmit CSI-Reference Signal (RS) for E-PDCCH. Accordingly, when CSI-RS exists in a PRB, the available resource of the PRB varies depending on whether the transmission is performed in the distributed transmission mode or the localized transmission mode.
Therefore, a need exists for a resource allocation method for control channel transmission in both the distributed transmission mode and the localized transmission mode.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.